With remarkable development of information technology (IT), a great variety of portable information communication devices has been popularized. As a result, in the 21st century, we are moving toward a ubiquitous society in which high-quality information service is possible regardless of time and place. Lithium secondary batteries are very important to realize such a ubiquitous society.
In recent years, design of electronic devices has been very important in consumers' choice of products and the electronic devices have been gradually miniaturized and thinned according to consumers' liking. To this end, there is a high necessity for miniaturizing and thinning a lithium secondary battery in order to minimize unnecessary waste of an internal space of each of the electronic devices. In addition, it is necessary for the lithium secondary battery to have various shapes corresponding to shapes of the electronic devices. In recent years, the demand for a curved battery, including a flexible battery, has increased.
In connection with this case, Korean Patent Application Publication No. 2012-0082808 discloses a curved battery. However, Korean Patent Application Publication No. 2012-0082808 only discloses the curved battery mounted in an external electronic device but does not disclose problems caused from the curved battery.